Modulating control system



May 16, 1944. F. A, GAUGER ETAL 2,343,969

MODULATING CONTROL SYSTEMS- Filed m. 5, 1939 4 Sheets-Sheet 2:

INVENTORS fm/v/r 4. 6141/65? BY [bk/W A 1/04/55 I? ZTTORNEY.

May 16 1944.

F. A. GAUGER EI'AL r 2,348,969

MODULATING CONTROL SYSTEMS Filed Aug. 5, 1939 4 Sheets-Sheet 3 INVENTORS fv/w/r 4. 6 4055? y 16, 1944- F. A. GAUGER ETAL MODULATING CONTROL SYSTEMS Filed Aug. 5, 1959 4 Sheets-Sheet 4 mNN INVENTORS Z W M i A Z WW Z Patented I6, 1944 MUDEJLATING @QNTRGL SYSTEM Frank A. Gauger, Milwaukee, and lid A. Jones, Shorewood, Wis; said Gauger, assignor to Min ncapolis-Honeywell i tor (Com 1:. 111

neapolis, a con-per ion or? Delaware Application August 5, 1939, Serial No. 2%,52il

Claims.

The present invention relatesto heating systems.

An object of the invention is to provide a modulating control system for heating in which a room thermostat is employed which in the preferred form has make and break contacts, and yet secures accurate modulation or modulated high low control of the fuel supply and maintains the temperature control within very close limits.

Another object is to provide a modulating control system which works accurately between maximum and minimum temperatures, in which all modulation occurs in a zone between these maximum and minimum temperatures, and in which the maximum and minimum temperatures may be so close that the change from one to the other is not perceptible by a, persons body.

Another object is to provide a modulating control system in which the flame of the burner comes on and stays on but is modulated to meet the present demand or any variation in the demand, the flame, however, being gradually reduced as the temperature approaches maximum, the temperature being under control at all times so that there is no possibility of wide variations in temperature.

Another object is to provide a heating system in which a modulating valve is controlled by a throttling thermostat, in which the throttling thermostat has additional heat added thereto which additional heat is controlled by an on and off simple type of thermostat in the preferred form, and in which the same thermostat also controls an on and off valve.

Another object is to provide a modulated heating system in which, in the preferred form, the

fuel flow is modulated by a pressure regulator functioning as a modulator under an artificial pressure built up and controlled by a throttling thermostat which is itself controlled by a simple type of on and off thermostat.

Another object is to provide a modulating system in which though the main or room thermostat makes and breaks its contacts repeatedly, or, if 'of the variable resistance type, varies its adjustment repeatedly, nevertheless-the main or on and off valve opens only once and thereafter the fuel flow is controlled by a modulating valve which does not open and close but which modulates in accordance with the demand, and which though the room thermostat makes and breaks contact, nevertheless secures a graduated'control or modulating control for the fuel flow so that there is no abrupt turning is gradually checked or increased in accordance with the demand.

Another object is to provide a modulating system of control in which a simple type of modulating valve of the order of a pressure regulator is employed, in the preferred form, and is caused to modulate under the control of an artificial pressure, such control by the artificial pressure being obtained by a throttling thermostat that has sumcient mass in proportion to its heat losses that an averaging effect is produced, so that although the room thermostat or master control comes on and off repeatedly, nevertheless the adjustment of the modulating valve is gradual.

Other objects are to provide a very simple modulating control system which employseasily produced relatively cheap parts and which is easy to adjust and install.

Referring to the drawings more particularly by reference numerals:

Fig. l is a diagrammatic view showing in general a heating system;

Fig. 2 is a sectional view through a pressure regulating and modulating valve showing a throttling thermostat carried by the modulating valve and forming therewith a unitary structure;

Fig. 3 is a fragmentary view showing a throttling thermostat positioned in the hood of a. furnace;

Fig. 4 is a diagrammatic view showing one' modification of the present invention;

Figs. 5, 6 and 7 are diagrammatic views showing other modifications of the present invention;

Fig. 8 is a diagrammatic detail of the coils in the magnetic valve of Fig. '7;

Fig. 9 is a fragmentary view of a further form of thermostat;

Fig. 10 is a fragmentary view of a modified modulating valve;

Fig. 11 is a sectional detail through the modulating valve of Fig. 10; and

Fig. 12 is a fragmentary view of a further form of modulating valve.

Referring to Fig. 1 of the drawings, I indicates generally a gas furnace which includes burners 2 and pilot lights 3. Hot air delivery'pipe's 4 leading to spaces to be heated are connected to the furnace I. A single cold air return 5 is shown leading to a main cold air return 6 which opens into the heating chamber of the furnace I.

A gas main I is connected to the burners 2. An electro-magnetic -main on and off valve 8 and a combined pressure regulator and modue lating'valve 9 are disposed in the gas main 1. A pilot supply line H) extends from a. point in the main I in advance of the on and off valve 8 to the pilot lights 3, an adjustment valve being provided at the tap with the main 1.

The valve 8 is connected by suitable leads to a room thermostat T for control thereby, electrical energy being supplied through a stepdown transformer H. The pressure regulating and modulating valve 9 is controlled in its modulating function by a gas thermostat H which includes a throttling gas valve i4 controlling a bleed line |5 leading from the valve 9 thereto,

the bleed line i5 continuing as line i6 from the thermostat l3 to the discharge side of the valve 3.

In Fig. 1, the gas thermostat i3 is shown positioned in the return duct 5; in Fig. 2, the gas thermostat is shown as part of the modulating valve 3, the thermostat being indicated by is and the valve by and in Fig. 3, the gas thermostat is shown within the bonnet of the fur nace I, the thermostat being indicated by I! and the valve by M.

The pressure regulating and modulating valve 9 (Fig. 2) includes an inlet chamber 2|, an outlet chamber 22, a valve seat 23, and a valve 24 having a shank screw-threaded into a small head 25 secured to the under race of a diaphragm 26. A small freely flexible diaphragm 2! is clamped between a lower casing portion 28 and the main casing of the valve 3. Centrally the diaphragm 21 is clamped between a shoulder .of the shank of the valve 249 and the lower portion of the head 25. The diaphragm 28 is clamped between the lower casing portion 23 and an upper casing portion 29, thereby providing a, lower diaphragm chamber 30 and an upper diaphragm chamber 3|. The upper chamber 3| is freely vented to the air at-32.

The upper casing portion 29 includes an integral upwardly extending neck 33 which is both externally and internally threaded. An adjusting screw 34 threadedly engages the internal threads of the neck 33 and bears against a compresslo'n spring 35, the lower end of the spring 35 being seated around the head. of a screw 35 which secures a large rigid disk 34 against the upper surface of the diaphragm 2G and which is in threaded engagement with the head 25. A look nut 38 secures the screw 34 in its adjusted position. A cover cap 39 threadedly engages the external threads of the neck 33 to conceal and protect the adjusting screw 34. A bleed line l5 (l5 in Fig. 1) taps the lower chamber 30 and leads to the valve 20. A line I6 leads from the valve 20 to the outlet chamber 22 of the valve 9.

A minimum flow by-pass duct 40 communicates the inlet chamber 2i and the outlet chamhex-22. An adjustable needle valve 4| controls the flow cross-section of the duct 40. A small duct 42 leads from the inlet chamber 2| into the lower chamber 33, an adjustable needle valve 43 being provided to vary the.fiow cross-section of the duct 42. The'maximum cross-section of the duct 42 is a small fraction of the maximum cross-section of the bleed line I5.

Referring to Fig. 4, there is disclosed a thermostat T1 which includes a bimetallic strip or portion 55 supporting an arm G6. The arm 45 is cut away in its central portion and is provided with notches receiving a snap spring strip a: to which is secured reverse bows 48. (For further are provided with opposing contacts 53 which are normally in engagement. The arm 52 is also provided with a contact 54 which is in opposed relationship to a stationary contact 55. A conductor 55 connects one side of the secondary of the step-down transformer l2 with the bimetallic strip 45. A conductor 51 connects the other side of the secondary with one terminal of the winding of the electro-magnetic valve 5. The other terminal of the saidwinding is connected by a conductor 58 with the stationary contact 53. The conductor 51 is also connected to one side of a small heat-coil or resistence 59' wound on the thermostat I3. The other side of the heat winding 53 is conected by a conductor 60 with the stationary contact 55.

Referring to the modification shown ,in Fig. 5, there is disclosed a room thermostat T: which includes a spring arm 5| carrying a second spring arm 52. The arms 5| and 52 have contacts 63 and 64, respectively, at the free ends thereof which cooperate with stationary contacts 55 and 56, respectively, mounted in opposed relation thereto. A conductor 51 connects one side of the secondary of the transformer l2 to the stationary contact 55, the other side of said secondary being connected by a conductor 68 to one terminal of the winding of the electromagnetic on and off valve 8. A conductor 59 connects the other terminal of the said winding to one terminal of an anticipating heat coil 10, the other terminal 19 of the coil ll! being connected by a conductor to the stationary contact 55. A conductor 12 connects a, bimetallic portion H of the thermostat T: with one side of a heat coil 13 surrounding the gas thermostat l3. A conductor I4 connects the other side of said coil 13 to a movable spring contact strip 15 biased from and normally out of engagement with a stationary contact I5 mounted on the valve 8 as a support. The valve 8 is provided with a projecting rod or plunger ii of insulating material which engages the strip 15 and which maintains the strip 15 in engagement with the contact 16 when the valve 5 is open. A conductor 18 connects the stationary contact I5 to the conductor 59.

Referring to Fig. 6, there is shown a thermostat T3 which includes a bimetallic portion 8| having an integral spring arm 82 to which is secured asecond spring arm 83. The spring arms 82 and have contacts 84 and 85, respectively, atgthe free ends thereof which cooperate with stationary contact 86 and, respectively, mounted in opposed relation thereto. A conductor 88 connects the secondary of the step-down transformer "l2 to the stationary contact 85. A conductor 89 connects the bimetallic portion 8| to one side of a heating coil 90 wound on the gas thermostat l3. A conductor 9| connects the other side of the coil 90 to a spring contact arm 92 mounted on the electromagnetic valve 8. The free end of the contact arm 92 is provided with a contact on eacH face, said arm 92 being biased to normally maintain the lower contact in engagement with a lower sta- V amnesia tionary contact at which is connected by conductors it and 95 to the other side of the secondary of the transformer it. One terminal of the winding of the electro-magnetic valve 8 is connected to the conductor 95, and, hence, to the said other side of the secondary or the transformer 52. The other side of the winding oi the valve 8 is connected by conductor at to the stationary contact at, and to' an upper stationary contact S'l supported on the valve d w and disposed in cooperative opposed relation to the upper contact carried by the contact arm 92.

Referring to Fig. I, there is disclosed a room thermostat T4. including a bimetallic portion 99 carrying a single arm so. The bimetallic portion at is connected to one side of the secondary oi thestep-down transformer ii. A conductor ltd connects the other terminal of the said secondany to the center terminal of a double winding oi th elective-magnetic valve 8 (Fig. 8).

is normally the operating winding to open the valve 8, and a second winding it? bucking the winding till which neutralizes the efiect of the The 30 double'winding includes one winding ml which ulating valve which includes a'casing I29 having therein a valve seat lid with whichcooperates a valve l3! spring-urged by a spring I32 into engagement therewith. A non-expansiole rod lit 5 is in engagement with the valve ill, the upper end of the rod its being attached to the upper end of a copper or other expansible tube ltd secured to the casing 529. A heating coil tilt is wound around the tube ltd in the manner of the heating coils about the gas thermostat it in the above described systems. A minimum flame adjustable icy-pass valve E35 communicates the inlet and outlet of the casing ma.

Operation The particular operation of the pressure regulating and modulating valve t (Fig. 2) is set forth in our co-pending application, Serial No. 2%,944 filed December 5,, 1938. It is suihcient for the present invention to point out that the valve 9 operates as'a pressure regulator until the restriction of the bleed line it, it by the gas valve it when under operation of the thermostat (13 reduces the flow section thereof to less than winding ltl when both windings are energized w the 130W Section o the d t M. w eup n t to permit the valve 8 to close. The upper winding tilt is connected by conductors Hi3 and-lu l to a stationary contact m5 disposed at one side of the spring arm 98. At the other side of the valve it functions as a modulating valve, an artiflcial pressure being established in the chamber st in excess of lower pressure. Were the line l t exhausted to atmosphere and not into the free end of the spring arm at is a. stationary cong Outlet Chamber 22 0f the Valve the Valve 9 tact Hi6 connected by a conductor Hill to a stationary contact the mounted on the valved. A second stationary contact ltd is located adjacent the stationary contact ltd. A movable conduc tive element lid, insulatively supported from a 3349 conducting spring strip Ml, bridges the stationary contactllid and tilt when the'strip Ml is in its uppermost position. The spring strip it t is mounted on the valve d and includes a contact on its upper face in opposed relation to a stationary contact M3 mounted on the valve it, said contact on the strip it i and the conductive element 5 it being normally out oi engagement with the stationary contact lit and the stationary contacts ltd and ml), respectively. A conductor 5 lit connects the contact tilt with the lower terminal of the bucking coil Hill. A conductor i Mi connects the stationary contact Elli to'one side of a heating coil M5 surrounding the gas their mostat Hit, the other side of the heating coil i it so being connected by a conductor lid to the upper terminal of the said secondary of the transiorrner ii.

in Fig. .9 there is shown part of a variable resistance thermostat including an arm d2 pro- 55 vided with a wiping contact ill in engagement with a resistance Mt, one end of the resistance being connected to the conductor dd. A step 909 limits the movement to the left of the arm 62.

The remaining elements of the system are of the @Q) heat, the valve it will remain fully open until exact form of Fig. 4.

Referring to Figs. 1c and ii, there is disclosed a modified modulating valve, generally indicated ltd, which is of the Sylphon type. The valve ltd includes a casing ill having therein a valve seat on fiaineby-pass lZ'l communicating the inlet and "to outlet of the casing ill is provided. A heating coil lid is disposed about the control bulb tilt which corresponds to the heating coil about the gas thermostat is in the above described syst.

In Fig. 12 is shown still another modified mit system shown in Fig. 4, with the thermostat in the position there shown the circuit through the electro-magnetic valve d is closed, and, hence, the valve d is open so that gas passes there-- through to and through the modulating valve Q to the burners i. The adjustable spring to of the valve ll (Fig. 2) is, of course, preadjusted to the desired maximum pressure to which gas will be supplied the burners 2. Assuming that the valve it is fully open, gas passes through the bleed duct tit into the lower chamber 3% and thence freely passes through the lines to, the open valve it, and the lines it to the outlet chamber Hence, the diaphragm till is subjected to burner pressure since, as pointed dut above, the cross-section of the lines it and it is many times greater than the cross-section of the bleed duct it. However, as heat isapplied to the thermostat it from the coil hi, the valve it throttles toward closed position until the crosssection oi the lines it, it is less than that oi the bleed duct 32 to build up an artificial pressure after the temperatureoi the room begins to rise. As the temperature of the space reaches a predetermined point, the movable contact ti l will engage the stati nary contact 55 through movement of the bi etallic portion ilt of the thermostat T1 to close the circuit through the heating coil or disposed about the thermostat it, a circuit in parallel with that through the coil of the valve 8. The artificial heat supplied the thermostat it by the coil 5d causes a throttling of the valve it and a consequent modulation action of the valve Q todecrease the supply of gas to the burner i. As the valve c throttles,

there is a slight decrease in temperature in the 1 a certain predetermined point.

space heated resulting in the opening of contacts 54 and 55 due to reverse movement of the bimetallic portion 45 thus opening the circuit of the heating coil 59. The thermostat l3 thereupon cools slightly to open the valve l4 and in ratio therewith the valve ii. The foregoing cycle is repeated, maintaining the temperature of the room at the desired level, and employing a continuous modulated flame at the burners 2.

Should the temperature of the space heated approach very close to the break temperature of the contact 49, the contacts 54 and 55 will remain in engagement so that artificial heat is continued to be supplied the thermostat lit by the coil 59 which effects closing of the valve 9. Minimum flame then obtains by gas supplied through the duct 40. Should heat supplied by the minimum flame be more than required, the arm at of the therinostat T1 will continue its movement to the left to snap the bow strip 45 over center from the stationary contact 59 into engagement with the stationary contact 5|, opening the circuit of the electromagnetic valve 8 which immediately closes, cutting off all gas supply to the burners 2. The on and oil valve 8 functions at two spaced temperatures only a few degrees apart, and, preferably, subtending a range not noticeable by a human body. Modulation occurs between the two extreme temperatures, starting slightly above the lowest temperature and terminating to give away to minimum flame just below maximum temperature. Due to the maximum rate of thermal radiation of the thermostat I3, no sudden violent jumping or moving of the valve 9 occurs, there being instead a floating action. The thermostat I3, of course, also responds to the temperature of the air in the cold air return or to the temperature in the bonnet of 'the furnace when disposed in these places, but is adjusted in accordance therewith.

It is manifest, therefore, that modulation is secured by the system shown in Fig. 4, even though a simple type of make and break thermostat T1 is employed.

The auxiliary contacts 53 of the thermostat T1 comprise means for breaking the circuit of the heating coil 59 during any time that the temperature of the space heated remains past In summer weather, the arm 46 will be to the left with the bow spring 41 permanently in contact with the contact 51. Continued movement of the arm 46 to the left due to the warm weather will open the contacts 53 and break the circuit of the heating coil 59. Hence, in summertime, both the circuit of the valve 8 and "the heating coil 59, remain open.

Particularly considering the operation of the system shown in Fig. 5, the thermostat T2, 9.8 the thermostat II moves counterclockwise when cooling and clockwise when subjected to heat. The relationship of the movable contacts 83 and t4 and the stationary contacts 65 and S8, respectively, is such that in movement counterclockwise, the movable contact 63 first engages the contact 55, the movable contact 64 engaging the contact 56 upon further movement of the thermostat T2. Obviously, in clockwise move ment, the movable contact 64 breaks with contact 66 first.

assaece the thermostat T2 moves clockwise disengaging the contact 64 from the contact 66, an action hastened artificially by the. heat coil 14. A holding circuit including the bimetallic portion II, the conductor 12, the heater coil II, the conductor 14, the contact strip 15, the stationary contact 16, the conductors I8 and 69, the coil of the electro-magnetic valve 8, the conductor 88, the secondary of the transformer I2, the conductor 61, the stationary contact 85, the movable contact 63, and the spring arm 6| maintains the electro-magnetic valve 8 in open position.

However, the coil I3 supplies artificial heat to the thermostat i3 which effects throttling of the valve I4 and therethrough the valve 9. Should the temperature continue to rise, the throttling will be complete to the degree of minimum flame as above described in connection with Fig. 4. Should the temperature of the room drop but slightly, the thermostat T2,, will move counterclockwise reengaging movable contact 64 with contact 66, shorting-out the coil 13, and permitting cooling of the thermostat IS with resulting opening to a-greater degree of the valve I which permits more gas to reach the burners 2. The aforesaid cycle is repeated, maintaining the predetermined temperature for the room. Should conditions raise the room temperature beyond that at which the contact 63 opens, then contact 63 is moved out of engagement with the contact 65, interrupting the whole electrical circuit to close the electromagnetic valve 8. I

It is to be observed that the heating coll ll functions only on the cold setting of the space thermostat T2, during a relatively high time setting of the valve and is an anticipating hat.- er. .A desirable feature of heat anticipation on the cold setting of the thermostat is the prevention of .excess heat storage in a furnace which would override the predetermined roomtemperature setting and the thermostat contact breaksetting regardless of subsequent reduction of flame. The heating coil III will not be energised unless the thermostat T248 in its cold position and is endeavoring to secure higher flame operation.

Particularly considering the operation of the system shown in Fig. 6, the operation of the thermostat Ta is the same as the thermostat '1': shown in Fig. 5 and above described. Assuming a fall in temperature in a room being heated, counterclockwise movement of the thermostat '1; first engages movable contact 44 with stationary contact 86 which immediately completes the circuit through the heating coil 04 surrounding the gas thermostat l3, artificially supplying asntoeo Zjbut immediately thereafter throttling or modulation of the'valve 9 occurs as a result of the v previously assumed position of the valve Il.

Movement of the valve 8 to open position effects closing of the contact arm 92 with the stationary contact 91 which short circuits the heater Ta and breaking of the contacts 85 and 81. The

latter, action permits renewal of the circuit through the heater coil with resulting artificial heating of the thermostat I3. The foregoing cycle is repeated, maintaining the predetermined room temperature. Should the room warm beyond the high break temperature of the thermostat T3, the clockwise movement of the thermostat T3 breaks engagement between the contacts 84 and 88 to deenergize the whole circuit, thereby closing the valve 8. The valve 8 is maintained in open position during the modulation cycles by the holding circuit which is effective when the contact is out of engagement with the contact 81 although contacts 84 and 88 are engaged.

Particularly considering the operation of the system shown in Fig. 7, the thermostat T4 is of the single arm type. As mounted, a drop in temperature effects clockwise movement and the application of heat causes counterclockwise movement of the thermostat T4. Assuming a drop in temperature in a room being heated, the

thermostat T4 will move clockwise engaging one contact with the contact I05 establishing a circuit through the upper coil of' the electric-magnetic valve 8, opening the valve 8 and permitting a full flow of gas to the burners 2. The opening of the valve 0 effects movement of the strip III into engagement with the stationary contact I I3 and the conductive element I I0 into bridging engagement with the stationary contacts I08 and W9. Upon the resultant temperature rise in the room, the thermostat T4 moves counterclockwise breaking the aforesaid contact between the arm 98 and the stationary contact I05. However, the valve 8 remains open due to the,establishment of a holding circuit from the upper side of the transformer I2 through the conductor 8, the heater coil I I5, the conductor I I4, the stationary contact II3, the contact strip III, the conductor I03, the upper terminal of the upper coil IOI of the electro-magnetic valve 8, and the conductor I00. Due to the action of the gas thermostat I3 under effect of the heater coil II5, the valve I4 and the valve 9 throttle to modulate the fuel flow to theburners 2. Failing the attainment of maximum temperature, the thermostat T4 moves clockwise to engage the stationary contact I05 thereby short circuiting the heater coil II5 permitting cooling of the thermostat I3 with resultant opening of the valves I4 and 8 the conductor I00 back to the'said secondary.

However, since the coils IOI, I02 '(Fig. 8) are so wound as to buck-each other for neutralization,

such neutralization occurs and the valve 8 closes by gravity, stopping the fl 'ow of may to the burners 2.

mer, the arm 98 of the thermostat T4 is in con- It is manifest that in warm weathenias ins'um; H

tact with the stationary contact I06 establishing the circuit aforesaid. But the circuit of the heater coil II5 will not beclosed since the valve 8 v ,is in closed position and the contact strip III. I

depressed by virtue thereof. 7

It is manifest from the foregoing descriptions of operation that in all forms of the invention,

the circuit for the respective heating coil for the gas thermostat I3 is.not energized in summer weather although no special setting and consequent care on the part of the user is required. In the systems shown in Figs. 4 and 7, specific means have been provided to prevent such energization and in the systems shown in Figs. 5 and 6. the respective arms of the thermostats are out of engagement with both contacts during warm weather.

It is to be particularly pointed out that the position of the gas thermostat I3 is immaterial as regards the present invention, and, hence, it may be disposed in the cold air return (Fig. l) in the bonnet of the furnace (Fig. 3), or elsewhere as choice and circumstances dictate. In' the systems shown in Figs. 4-7, a make and break thermostat is employed, and effective accurate modulation is obtained therewith as aforedescribed.

However, a variable resistance thermostat of the nature of that shown in Fig. 9 may be employed.

The preferred form of pressure regulating and the valve I20 of Figs. 10 and 11, or the valve of Fig. l2 would simply replace the valve 9 together with the gas thermostat I3 and its respective heater in the systems shown in Figs. 4-7.

It is to be understood that the foregoing description and the accompanying drawings have permitting a greater flow of fuel to the burners 2.

been given by way of illustration and example and not for purposes of limitation, the invention being limited only by the claims which follow.

We claim: l. A heating system including an electrically actuated on and off valve, a modulating valve, said valves being in a fuel line 'to a burner, a thermostat disposed in a space to be heated, said thermostat including two contacts adapted to consecutively make and consecutively break, a thermostat and valve for controlling saidmodulating valve, a power source, an actuating electrical circuit through said two contacts, the power source and the electrical valve actuator for opening said electrical valve, a-holding circuit through the firstcontact to make the power source and the electrical valve actuator operable when said second contact is open, means to complete the holding circuit actuated by opening of the electrical valve, a heating coil in the holding circuit disposed about ,the thermostat of the'said thermostat and valve, and a heating coil in the actuating circuit disposed in adjacent relationship to the space thermostat, said latter 'coil having a erated by closure of the second contact and being adapted to open the said second making contact of the space thermostat prematurely to prevent heat overrun and consequent opening of the first making contact to open the holding circuit.

2. In a mechanism of the kind described, a fuel flow control means operable to a maximum flow limit and to a minimum flow limit, a space thermostat operable to a cold position and a warm position, an anticipating heater for the thermostat energized only when the thermostat is in cold position,'modulating means to eflect' operation of the fuel flow control means toward the sive device adapted to operate the modulating.

means toward flow-restricting position upon increase in heat thereat, a heater for the heatresponsive means, a first circuit including the heater of the heat-responsive means to effect restriction of flow, and a second circuit including the thermostat in cold position and the anticipating heater adapted to at least reduce energization of the heater of the heat-responsive means to cause the fuel flow control means to effect increase of flow.

4. In a' heating system, a fuel supply modulat-. ing means, electrical power means to operate the modulating means, said electrical means being adapted to operate the modulating means to restrict fuel flow upon increase of power appliedthereto, and to eflect operation of the modulating means to increase fuel'i'low upon reduction of power applied thereto, a thermostat movable 1 from a cold to a warm position, an anticipating heater for the thermostat energized when the thermostat is in cold position and at least sub stantiallyineflective when the thermostat is in warm position, a first circuit through the electric power means to supply predetermined power thereto to eifect reduction of fuel now. a second circuit closed by operation of the thermostat to cold position, and including the anticipating heater, said second circuit being in parallel with the first circuit and by said parallelism acting to shunt the first circuit at least partially, whereby to reduce the'power supplied to the electrical power means and effect increase of fuel flow.

5. In a heating system, a fuel supply modulating means, including a heat-responsive element adapted to efiect decrease of fuel flow upon application of heat thereto and increase of fuel flow upon reduction of heat applied thereto, an electrical heater in heat-transfer relation to the heat-responsive element, a space thermostat movable from a cold to a warm position, an anticipating heater for the thermostat energized when the thermostat is in cold position and at least substantially ineifective when the thermostat is in warm position, a first circuit through the electrical heater to supply predetermined power thereto to effect reduction of fuel flow, a

second circuit closed by operation of the thermostat to cold position, .and including the anticipating heater, said second circuit being in parallel with the first circuit and by said parallelism acting to shunt the first circuit at least partially whereby to reduce the power supplied to the electrical heater and eifect increase of fuel flow.

1 FRANK A. GAUGER.

EDWIN A. JONES. 

